Mix 1½ tubs of the Boursin with the ham and spring onions, then use to sandwich together the bagels. Cut these in half to create semi-circles. Dip the bagel halves into the egg, soaking them well, then put upside-down into a large, round, buttered baking dish. Pour the rest of the egg mixture over and leave to soak for 20 minutes. Just before baking, flip over the bagels so they’re top-side up, spoon over little blobs of the remaining Boursin, then bake for 25-30 mins or until just set and golden. Sprinkle with chopped chives and serve warm.